Three-phase fluorescent lighting system



July 13, 1954 cRAlG 2,683,798

THREE-PHASE FLUORESCENT LIGHTING SYSTEM Filed May 9, 1951 lNVE/VTORFREDER/CK E CRAIG WM y,

F/G. Z J? Arr'rs Patented July 13, 1954 THREE-PHASE FLUORESCENT LIGHTINGSYSTEM- Frederick E. Craig, Lynn, Mass. Application May 9, 1951, SerialNo.'225,350

I 11 (Jlaims. 1

This invention relates to lighting apparatus employing light sources ofthe electric discharge type. In the illustration disclosed in thisspecification it is applied to apparatus in which the light sources arefluorescent lamps; and that fact is indicated by the title. However, theinvention is applicable to all situations in which electric dischargelight sources of any character are connected in the several phases of athree phase alternating current, and its scope is to be construedaccordingly.

The objects of the invention include that of eliminating flicker andstroboscopic eliect in the operation of such light sources with greaterefficiency and economy than has been possible with apparatus heretoforeknown; and to provide a lighting fixture for operation by three phasealternating current with a compact and economical ballast by which lightof substantially uniform intensity and continuity is obtained. A relatedobject is to provide a self contained ballast for use in the operationof gas type lamps in a three phase circuit in which the transformers forall of the lamps have a single continuous magnetic circuit and all,

together with associated equipment, are contained in a single case.

A further object is to provide circuit connections between the parts ofthe ballast and the sockets which removably contain the lamps, sodisposed as to deliver current to the lamps of sufficiently high voltageto insure starting, and at the same time to eliminate possibility ofdangerous voltage being passed through a person who may carelesslyhandle a lamp when inserting it into its high voltage socket.

I am aware that it has been proposed heretofore to furnish a steadylight by connecting three single phase gas filled lamps in the severalphases of a three phase circuit; but, to the best of my knowledge andbelief, no combination of such a collection of lamps with a three phaseballast in one fixture has ever been made or proposed.

My invention consists in a combination by 4 which the objectsprecedently set forth are realizedand, in the preferred embodiment ofwhich, three single phase lamps are mounted on a single fixture and areconnected with a ballast in the same fixture, such ballastincluding-transformers for the several lamps having a single continuousmagnetic circuit, and reactors, all cempactly'assembled and encased as aunit subcombination and the parts of which are connected withthe socketsof the lamps insuch v diagram, Fig. 4.

2 manner as to eliminate danger from electric shock to persons who maycarelessly handle lamps while inserting them into the high voltage lampsockets.

A further object of this invention comprises an arrangement by whichshould any of the three single phase lamps be removed from the fixtureor become otherwise inoperative, the other lamp or lamps will remainlighted with the same brilliance as though all three lamps were inoperation.

In the accompanying drawings Fig. 1 is a perspective view of a lightingfixture having three tubular gas filled lamps and including anembodiment of the other features of the invention;

Fig. 2 is aside elevation of the fixture shown in Fig. 1 andrepresenting by broken lines the casing of the ballast which iscontained within the lamp fixture housing;

Fig. 3 is a plan View of the ballast on a scale larger than that of thepreceding figures, showing the casing of the ballast in section on theline 3"3 of Fig. 2;

Fig. 4' is an electrical diagram showing the lamps and the parts of theballast connected with a three phase alternating current power sourceand including connections by which high voltage is removed from thecircuit whenever any lamp is removed from its socket;

Fig. 5 is a diagram somewhat similar to Fig. 4 but with the severaltransformer primaries arranged in delta.

Fig. 6 is an exploded view of the parts of a core with which thewindings of all of the transformers of the ballast are assembled so asto provide a single magnetic circuit;

Fig. '7 is a longitudinal section of the assembled core taken on line1-1 of Fig. 3 and shown on a larger scale.

Like reference characters designate the same parts wherever they occurin all the figures.

Tie fixture here shown comprises a canopy 10 adapted to be mounted onthe under side of the ceiling of a room or any other overhead structure.A housing I! is suspended from the canopy by tubular suspenders or stemsand It, through either of which electrical conductors can be passedto'the interior of the housing.

Projecting from the under part of the housing at the opposite ends aresockets in which the ends of tubular single phase lamps M, iii and 15are mounted. Two of these lamps are shown in Figs. 1 and- 2, and thethird is shown in the Those represented here are the commonly used gasfilled fluorescent tubes of the electric discharge type havingelectrodes sealed into both ends. The sockets for these tubes at one endof the housing are shown at l1, l8 and IS in Fig. 1, and those for thetubes 14 and I at the other end of the housing are shown at '29 and 2|.The third socket at this end is shown at 22 in Fig. 4.

A case for the ballast transformers and auxiliary equipment is shown bydotted lines at 23 in Fig. 2 as being contained within the housing llsuspended from the top wall of the housing. This ballast or transformercase is shown in detail in Fig. 3 with the transformers and associatedpower factor condensers and reactors assembled therein as a unitcombination. In the specific apparatus chosen for present illustrationof the invention, there are three transformers, of which the windingsare separately connected in the several phases of a three phasealternating current circuit and all the windings are combined with asingle iron core structure disposed to furnish a single continuousmagnetic circuit. The transformer windings are shown at 24, 25 and 26 inFig. 3 and the core structure is shown in detail in Figs. 6 and 7. Thelatter has elements passing through and embracing the windings and ismade of laminated parts and so designed as to permit easy assemblagewith the windings and provide uninterrupted paths for magnetic fluxwithin and around the windings. Power factor capacitors 27, 28 and 29,reactors 30, 3! and 32, and radio interference preventer condensers 33,34 and 35 are connected in circuit with the condensers, and all aremounted compactly in the case 23.

Reference is directed to the diagram in Fig. 4 for a showing of theconnections between these several electrical elements and the lamps. Thethree wires L L and L from a three phase alternating current source areled through the suspender l2 into the ballast case 23 and are connectedwith the transformer windings 24, 25 and 25, respectively. Thetransformers here shown are auto-transformers, having the primary andsecondary windings designated 13 and s, respectively. The primarywinding of transformer 24 is connected by a conductor 36 with the lowpotential socket ll of the lamp M, by a conductor 31 with one terminalof power factor condenser 21, and by a conductor 38 with one terminal ofthe radio interference prevention condenser 33. The secondary winding oftransformer 24 is connected by a wire 39 with the opposite terminal ofthe power factor condenser and by a Wire ii) with one terminal of thereactor or choke coil 30. The opposite terminal of the reactor isconnected by a wire ll with the opposite side of the condenser 33 and bya wire 42 with the high voltage socket 20 of the lamp l4.

The other transformer primary windings are connected by conductors 43and 44 with the low potential sockets of the lamps l5 and I5,respectively; the reactors 3! and 32 are connected by conductors 45 and56 with the high potential sockets of these lamps; and connectionsessentially like those first described are made between the secondarywindings of transformers '25 and 26 with the power factor condensers 28and 29 and reactors 3i and 32, respectively, while connectionsessentially like those first described are made between the primarywindings of transformers 25 and 26 with the condensers 28, 28, 34 and 35and betweenthe last named condensers and the reactors 3i and 32,respectively. All of the low potential lamp sockets have tWQ separatecontacts arranged to bear on the metal fitting on the low potential endof the lamp tube, which is connected with the electrode at that end ofthe lamp, when the lam is inserted into the socket. The severalcondenser primary windings are connected each with one of the contactsin the several sockets, as indicated by the diagram. In this diagram thepoints of connection of the conductors 36, 43 and 46 with the socketsi1, is and i5, respectively, represent one of the contacts in eachsocket. The other contacts of the sockets l1, l8 and is are in shuntedconnection with one another by a conductor t1 and branch $3.

With this mode of connection, the three transformers are connected in athree phase star circuit and the shunt 47, s8 is the center connectionwith the star. The metal terminal fitting of any lamp, when insertedinto its socket, bridges across the separated contacts in the socketand, when all of the lamps are in place, the star circuit connection ofthe three transformers is completed. When any lamp is removed, thecircuit between the condenser to which that lamp is related and thecenter connection is broken.

The core structure of the transformers, the cores of the reactors, andthe metal shells in which the power factor condensers are encased areall grounded on the case 23; an insulated conductor for that purposebeing shown at 59 in Fig. 3, being connected to the case at 5% andhaving branches connected. with the several cores and transformershells.

An important safety feature is afforded by the circuit connections ofthe ballast with the low voltage sockets of the lamps. The dangeragainst which this safety feature protects is this: Burned out lampsneed to be replaced from time to time, and a person making such areplacement could, by inserting one end of the new lamp into the highvoltage socket while holding the other end of the lamp and beingconnected to ground, cause the lamp to start and be subjected todangerous voltage if the full voltage were then applied to the socket.Such handling of a lamp in being mounted in its sockets is very liableto occur. I have removed the possibility of danger resulting fromhandling of a lamp in this manner by the circuit connections here shown,which cause the voltage in the circuit of any lamp to be reduced to asafe degree when the lam is removed. Thus, assuming, for instance, thatthe lamp 1 3 has been removed, then no current passes through theprimary winding of the transformer 24 which is connected to that tube.Consequently the voltage is not stepped up in the secondary Winding ofthat transformer, but the voltage from the power line which passesthrough the secondary winding and through the reactor 38 is too low toenergize a lamp, and the person who may place one end of a lamp in thesocket 2! while handling it in the manner described is insulated-againstany passage of current through his body.

The core structure of the ballast is. made of numerous originallyseparate parts constructed for easy assemblage with prewound wire coilsand with each other into a unitary structure having magnetic continuity.In the illustrated embodiment, the individual pieces are cut from sheetiron .026 inch thick. Most of them have an outline similar to the letterE, consisting of a trunk portion a and three lateral branches 1), c and01 extending to the same side from the ends and middle of the trunkportion. A smaller proportion of these pieces are of straight bar formhaving the same length and width as the trunk poraeeavee tions a.Groupsof three pieces eachareeassembled :in stacks. with-each wire coiland with-their branches overlapped. Thus the. group ot-pieces designated5|] in Fig. 6 is assembled with .thegroup designated- 5| sothat their.branches: overlap and-the middle branches ofboth pass through thecentral. openings of thecoils. while the. end branches embrace thecoils. Other. like groups are stackedonthe two groups. above. describedand interleaved with the coils until a core. of theprescribedthicknesshas beenbuilt ups other groups-iband 53 are similarlystacked up. in assembled relation with thewirecoil of a secondtransformer. The/trunk. portions of'the groups in each stack arespacedapart fromone anothen by the thickness of the: overlappingbranches, andthe trunk: portions: of the stacked up-groups52 areinsertedintothe spaces between the=-trunk portions of the stacked groups 5!.Groupsof-bar shaped pieces 54 are inserted between-thetrunkportions ofthe groups 50-.

A thirdsetofg-roups Ea and 56- of E shaped pieces arestacked-inassemblage'with the third transformencoil in the sameway, and the trunkportions ofthe groups. 55 are inserted in the open spaces between thetrunk portions of i the groups53= Finally,- groups of bar'shaped pieces51 areinserted'inthe-spaces between the trunk portions of the-groups 56.Then'the whole assemblage makes a: substantially solid" laminatedstructure, as shown' in section in Fig. '7.

In; the winding 0f the transformercoils, the secondary coil is a woundoutside of the primary coil so that it is situated next to the portionsof the -iron-core by-which it is embraced. Also the; coils of one-of thetransformers are wound oppositely to the-winding of theother-transformercoils. Thus-the-transformers 24 and ZS may be wound-clockwisei as toboth the primary and secondary windings; and the transformer 25 woundcounterclockwise; Orviceversa. This is an important factor, as itsuppresses the third harmonic; preventing vibration.

The cores 58', 59-and60 of the several reactors are; also provided withatrunkportion and" three lateral branchesaround and=between whichtheseveral coils are located; The several cores are associated with barsSl,62'and lid-which bridge across the branches of the cores and completethe magnetic circuitsthrough the-latter-. Gaps, which may bevariedinwidth from zero to a limited'maximuin value, are providedbetween the bars andtheadjacentbranches of the cores. By adjustment ofthe width of these gaps, the strength of the currentpassing through thereactor coils may be varied and adjusted. Onceadjusted, the gaps are preferably filled with solid insulation and] thereby 'made permanent.

All of-the parts herein described, i; e., ballast, condensers andreactors, are compactlyassembled in thecase 23 and made fast therein.Although no specific fastening means are shown in the drawing, itmay beunderstood that any mechanical fasteners or other means suitable forthe. pu pose can e. sed.

By assemblingthe transformer windings of all three phases ofthe powercircuit in association with what is in effect a. single core, a muchmorecompactiand enicient ballasthas been made, with a very-large saving ofcost. These factors; ofefficiency, economy. and convenience are enhancedbythe assemblage of all.of;the parts ofgtheapparatus (ballast,condensers; and. reactors com pactly in a single case as aself-contained unit.

In this apparatus the transformers are designed to stepv upvthel.electromot-ive force to 600 volts when the .current. isetu-rned on,which is sufiicient tostart the lamps After starting. the voltage dropsto a. continuously. operating value. The. reactors cut down the currentto the prescribed strength, which. may be varied, as previously stated,by adjustments-of the. gap between the cores of'these reactors and=theirassociated-armature bars. The normal operating current is300milliamperes. and it can be increased by this adjustment upto 500milliamperes.

In Fig. -5-.the threetransformer primary windings. areshown. arrangedin. delta, the line Ll being connected}. to-the mid-point of theautotransformer 24. while the opposite end of the primary-ofthertransformer isconnected through lead 65 andthe socket I! with themid-point of the transformer 26: and through loads 65 to the line L3;Similarly the opposite end of the primary of thetransformer 26 isconnected. through the lead 61, socket l9. and lead 58 tothe line L2 andtothemid-point of the transformer 25, whilethe. opposite end of theprimary of the transformer '25 iseonnectedthrough leads. 69 and 43,socket l8 and lead 10 with the line LI and to the midz-point of'thetransformer 24. The ballast, condensers, and-reactorsare connected precisely as. in- Figure. 4; With this. arrangement shown in Figure 5,failureor omission of one or more of the lamps in no way interferes withthe operation Many of the others, each of which has impressed on itsterminalsat all times the voltage difierential between two of the linesLI, L2 and L3.

This application is a. continuation-in-part of my application. SerialNo. 110,725, filed August 17, 19.49, for Three Phase FluorescentLighting System.

While I have given specific values for some of the features of thecombination herein il1ustrated, it is. to beunderstood that these valuesare not limiting, but they may be varied widely within the limits knownto be safe in this art. The principlesof the-described embodiment areapplicable with modifications understood by those skilled in the arttofixtures designed for fluorescent lamp tubes of all the variouslengths and diameters employed in practice.

I claim:

1. An electric lighting system comprising three single phase gasfilledlamps of the electric-dis charge type; a transformer having threeseparate sets of primary and secondary windings assembled with a singleiron core, connections for the flow ofcurrent between the separatephases of a threephasepowersupply source and the sew eral primarytransformer windings, individual connections from the-several primarywindings to the several lamps atoneterrninal, and-in iv-idualconnections between the several secondary transformer-windingsand theseveral lamps at the-opposite-terminal thereof, said windings of saidtransformer being arranged in tandem .nd the middle winding being in thereverse direct. tot-he direction of 'the other windings.

2. An electric-- lighting apparatus comprising three single-phasegasenlledlamps of the electric discharge-type, three auto-transformerunits in assembled relation; with alaminated ironst'ructure disposed;-to provide-- uninterrupted paths for magnetic fiuig around thetransformer windings, the primarywindingof each transformer'beingconnectedqwith one oftheconductcrs of a'three phase alternatingcurrentsupplydine and with the low potential terminal of one of the lamps,

7 and the secondary windings of the same transformers being connectedwith the high potential terminals of the respectively same lamps; suchconnections of each transformer with one lamp being separate from thecorresponding connections of each of the other transformers with theother lamps, the primary winding of the central unit being reverselywound to the other primary windings.

3. A three phase lighting apparatus comprising three single phase gasfilled lamps of the electric discharge type, high potential and lowpotential sockets in which the opposite terminals of the lamps aremounted, the low potential sockets each having two separated contactswhich are bridged across by the inserted lamp, three transformersconnected separately with the conductors of a three phase power supplycircuit, conductors leading from the primary windings of the sevcraltransformers to the low potential sockets of the several lamps, eachconnected to one of the contacts in the respective sockets, meansconnecting the other contacts of all of said low po tential socketstogether electrically, and connections for flow of current from thesecondary windings of the respective transformers to the Several highpotential sockets, one of said primary windings being in the reversedirection to the other primary windings.

4. A lighting fixture comprising three single phase gas filled lamps ofthe electric discharge type and three single phase auto-transformers,each primary transformer element being connected in series with onecontact of a two-cork tact lamp socket and the three primary transformerelements being connected separately to the separate phases of a threephase alternating source, the other contacts of said two contact socketsbeing connected separately to a difierent three phase alternating sourcefrom which the first said contact of the two-contact socket isconnected.

5. An electric lighting starting and controlling system comprising threesingle phase gas filled lamps of the electric discharge type and threesingle phase auto-transformers having separate sets of primary andsecondary windings, said primary windings being connected in star and toone terminal of a lamp and the corresponding secondary being connectedthrough a ballast unit to the opposite lamp terminal 6. An electriclighting apparatus comprising three single phase gas filled lamps of theelectric discharge type, a three phase ballast having three transformerunits provided with separate sets of primary and secondary windingsassem bled on a single core, each transformer winding being connected atits secondary terminals with the terminals of one only of said lamps,the intermediate terminal of each winding being connected to one of thephases of the supply and to the low voltage terminal of one of the otheror" said lamps.

7. An electric lighting apparatus comprising three single phase gasfilled lamps of the electric discharge type, a three phase ballasthaving there transformer units provided with separate sets of primaryand secondary windings assembled on a single core, each transformerwinding being connected at its secondary terminals with the terminals ofone only of said lamps, the intermediate terminal of each winding beingconnected to one of the phases of the supply and to the low voltageterminal of one of the other of said lamps, said coils being arranged intandem on said core, one of said coils being wound in the reversedirection to the winding of the other two coils.

8. A lighting fixture comprising a housing, three single phase gasfilled lamps of the electric discharge type mounted on said housing, anda three phase ballast including three transformer elements mounted insaid housing and having a single iron core, each transformer elementbeing connected at its terminals with terminals of one only of saidlamps, and the several transformer elements each having terminalsconnected separately to the separate phases of a three phase alternatingcurrent source.

9. An electric lighting system comprising three single phase gas filledlamps of the electric discharge type, a transformer element having threeseparate sets of primary and secondary windings assembled with a singleiron core, connections for the flow of current between the separatephases of a three phase power supply source and one terminal of theseveral primary transformer windings, individual connections from theother terminal of the several primary windings to the several lamps atone terminal of such lamp, and individual connections between theseveral secondary transformer windings and the several lamps at theopposite terminal of such lamp.

10. An electric lighting apparatus comprising three single phase gasfilled lamps of the electric discharge type, a ballast having threetransformer units in assemblage with a unitary laminated iron core, oneterminal of one of the primary windings of the several transformer unitsbeing separately connected with the several conductors of a three phasealternating supply line, the opposite terminals of the primary windingsof the several transformer units and one terminal of the secondary ofthe said transformer units being individually connected with oneterminal f the several lamps, and the other terminal of the secondarywindings of the several transformer units being individually connectedwith the opposite terminals of the respective lamps. 11. In combination,means for supporting three gas filled lamps of the electric dischargetype and a controlling circuit for said lamps including a ballastcomprising three transformer coils, a laminated iron structuresupporting said coils and disposed to provide a continuous magneticcircuit around each and all of said coils, each transformer coil beingconnected to one termiml of one of said lamps and with one conductor ofa three phase alternating current supply circuit separate from theothers, said coils being arranged in tandem on said laminated ironstructure and the middle'coil being wound in the reverse direction tothe windings of the other two coils.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,010,849 Dorgelo Aug. 13, 1935 2,020,707 Uyterhoeven Nov. 12,1935 2,327,755 Abernathy Aug. 24, 1943 2,342,570 Biller Feb. 22, 19442,359,057 Skinner Sept. 26, 1944 2,461,957 Berger Feb. 15, 19492,472,882 Berger June 14, 1949 2,485,398 Mandi Oct, 18, 1949 2,491,858Hehenkamp Dec. 20, 1949

